[Cauhtemoc]

Quote:

Originally Posted by chesebert I am not sure swapping the opamp would bring much benefits (for the amount of efforts involved; had they socketed those damn chips it would have been much easier, alas that's not the case)

Bypassing the coupling capacitors and changing the opamps will yield a substantial improvement.

Quote:

Originally Posted by Herandu The 5532 and 5534 have a maximum input level of 0.6V, before a set of back to back diodes clamp any signals above that level. Most good DAC chips produce an output above that 0.6V level however, so the input signal to a 5532 would have to be reduced in gain prior to it being fed to a 5532. If you don't reduce the gain the 5532 will clip the signal.

They have a maximum differential input level of 0.6V. Under normal working conditions, the differential input level is always 0V.

 

[regal]

Quote:

Originally Posted by ezkcdude /img/forum/go_quote.gif You don't need to spend thousands of dollars to get a great sounding DAC. You can build one yourself for a couple of hundred that will sound very respectable.

NOS or PCM2704 USB , not a higher end DAC we are talking about.

This is about the most basic OS current out DAC you could build:

http://www.mypage.tsn.cc/dakiller/dac1/dacs.png


Would you want to perf board this ?

All said and done you are looking at $500 by the time you make the PCB and buy all the components. Factor in your time and you would be much better off buying a commercial product.

 

[n_maher]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif Please list the Wadias and Meridians that you've heard.

Still waiting regal, I'm in the market for a high-priced Cmoy and need your advice.

 

[ezkcdude]

Quote:

Originally Posted by regal /img/forum/go_quote.gif This is about the most basic OS current out DAC you could build: http://www.mypage.tsn.cc/dakiller/dac1/dacs.png Would you want to perf board this ? All said and done you are looking at $500 by the time you make the PCB and buy all the components. Factor in your time and you would be much better off buying a commercial product.

I know it well. I guess you haven't clicked on the link in my sig.

 

[Herandu]

Quote:

Originally Posted by Cauhtemoc /img/forum/go_quote.gif Bypassing the coupling capacitors and changing the opamps will yield a substantial improvement. They have a maximum differential input level of 0.6V. Under normal working conditions, the differential input level is always 0V.

Assume a signal input square wave with dV/dt of 250V/ms and 2V (i.e. CD output level) peak amplitude. The input waveform will reach 2V/250V/ms or
8ns, while the output will have changed (8×10-3) only 56mV. The
differential input signal is then (VIN-VO) RI/RI+RF or approximately
1V. The diode limiter will definitely be active and output distortion will
occur; therefore, VIN has to be <0.6V at all times.
If as you claim that under normal working conditions the differential input level is always 0V, then the DAC is not giving out any sound.

 

[Cauhtemoc]

Quote:

Originally Posted by Herandu Assume a signal input square wave with dV/dt of 250V/ms and 2V (i.e. CD output level) peak amplitude. The input waveform will reach 2V/250V/ms or 8ns, while the output will have changed (8×10-3) only 56mV. The differential input signal is then (VIN-VO) RI/RI+RF or approximately 1V. The diode limiter will definitely be active and output distortion will occur; therefore, VIN has to be <0.6V at all times.

If you have a slew rate of 0.25V/us (or 250V/ms), it will take 8 us for it to change 2V. And where does the 56 mV come from?

Let's take another example. Assume that we have a delta sigma DAC capable of 192 kHz output (like the AK4396). The maximum voltage the DAC can swing is 5V, and the minimum time it can do this is 1/192000, or about 5us. This gives a maximum slew rate of 1V/us. In reality it will be perhaps 10% of this at most, but this is the theoretically highest slewrate the DAC can achieve. Now let's look at the NE5534, it has a slew rate of 13V/us.

Quote:

Originally Posted by Herandu If as you claim that under normal working conditions the differential input level is always 0V, then the DAC is not giving out any sound.

Do you know how an opamp works? We are working with audio frequencies of up to 20 kHz. Compare this to the 10+ MHz bandwidth of an opamp. For all intents and purposes, the differential input voltage (that is, the difference between the inverting and non-inverting input) will be 0V.

 

[Herandu]

Quote:

Originally Posted by Cauhtemoc /img/forum/go_quote.gif If you have a slew rate of 0.25V/us (or 250V/ms), it will take 8 us for it to change 2V. And where does the 56 mV come from?

Sue, but I used a slew rate of 250V/mS, not 0.25V/us.
Didn't you understand where the 56mV came from? Read what I wrote again, and take the blinkers off this time.

Quote:

Let's take another example. Assume that we have a delta sigma DAC capable of 192 kHz output (like the AK4396). The maximum voltage the DAC can swing is 5V, and the minimum time it can do this is 1/192000, or about 5us.

Are you sure you are not using the calculation of a NOS DAC instea dof a Delta Sigma DAC?

Quote:

Now let's look at the NE5534, it has a slew rate of 13V/us.

I had no idea the 5534 had a slew rate of nearly twice that of the 5532.



Quote:

For all intents and purposes, the differential input voltage (that is, the difference between the inverting and non-inverting input) will be 0V.

I think you should have a look at the diagram of a 5532. The diodes are back to back across the inverting and non-inverting inputs. Try what you say and insert a 0.6V signal into the 5532 and what the output on a scope.

 

[Cauhtemoc]

Quote:

Originally Posted by Herandu Sue, but I used a slew rate of 250V/mS, not 0.25V/us.

Let's get a few things straight. ms means milliseconds, 1/1000 of a second. us means microseconds, 1/1000000 of a second. Thus 1 ms equals 1000 us, and thus 250V/ms equals 250V/1000us, which equals 0.25V/us.

Quote:

Originally Posted by Herandu Didn't you understand where the 56mV came from? Read what I wrote again, and take the blinkers off this time.

What you said earlier makes no sense.

Quote:

Originally Posted by Herandu Are you sure you are not using the calculation of a NOS DAC instea dof a Delta Sigma DAC?

The type of DAC makes no difference. The fact is that 1V/us is the highest you will ever see from a 192 kHz DAC regardless of the actual type of DAC. And at 20 kHz it will only be 0.1V/us.

Quote:

Originally Posted by Herandu I had no idea the 5534 had a slew rate of nearly twice that of the 5532.

The NE5532 has a typical slew rate of 9V/us. This is less than the NE5534, but still way, way more than needed.

Quote:

Originally Posted by Herandu I think you should have a look at the diagram of a 5532. The diodes are back to back across the inverting and non-inverting inputs. Try what you say and insert a 0.6V signal into the 5532 and what the output on a scope.

I repeat my earlier question, do you know how an opamp works? The difference between the inverting and non-inverting input will always be 0V. If necessary I will post a simulation to help you understand.

 

[Herandu]

Quote:

Originally Posted by Cauhtemoc /img/forum/go_quote.gif I repeat my earlier question, do you know how an opamp works? The difference between the inverting and non-inverting input will always be 0V. If necessary I will post a simulation to help you understand.

Please do. Mind you, I work with real life application, but let's have a laugh for a change. By the way, I didn't want to knit pick on the other points. I might give away too much R&D secrets..

 

[Cauhtemoc]

Quote:

Originally Posted by Herandu Please do. Mind you, I work with real life application, but let's have a laugh for a change. By the way, I didn't want to knit pick on the other points. I might give away too much R&D secrets..

Alright, if you want a real life example, take a NE5534 (or any other opamp) and make any of the example circuits given here:

Operational amplifier applications - Wikipedia, the free encyclopedia

Hook it up to a function generator (or two in the case of the differential amplifier), and take a scope and look at the inverting and non-inverting inputs. You will see that they are exactly the same, even at frequencies much higher than audio.

 

[d-cee]

Quote:

Originally Posted by Herandu /img/forum/go_quote.gif Please do. Mind you, I work with real life application, but let's have a laugh for a change. By the way, I didn't want to knit pick on the other points. I might give away too much R&D secrets..

whose R&D???

LOL

 

[regal]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif Still waiting regal, I'm in the market for a high-priced Cmoy and need your advice.

Put a big price tag on a PCM2704+cmoy and pay for a 3 page review in Stereo Times that praises the excellent jitter rejection and people will fall in love with the sound.

 

[Herandu]

Quote:

Originally Posted by d-cee /img/forum/go_quote.gif whose R&D??? LOL

He he LOL

 

[n_maher]

Quote:

Originally Posted by regal /img/forum/go_quote.gif Put a big price tag on a PCM2704+cmoy and pay for a 3 page review in Stereo Times that praises the excellent jitter rejection and people will fall in love with the sound.

So what you're really saying is that you've never heard a Meridian or Wadia and your previous comment was based on an assumption, thanks for that.

 

[regal]

My friend had a wadia (830?) we did a soundcheck with its analog out vs digital out to his levinson 36. The grain in the upper mids on the wadia was very obvious vs. the Dac in both our opinions.
As a transport though it was solid. This was years ago and I haven't pursued listening to another Wadia since. Maybe the are better now ?